Some businesses, particularly banks, are regularly faced with large amounts of currency which must be organized, counted, authenticated and recorded. To hand count and record large amounts of currency of mixed denominations requires diligent care and effort, and demands significant manpower and time that might otherwise be available for more profitable and less tedious activity. To make counting of bills and coins less laborious, machines have been developed which automatically sort, by denomination, mixed assortments of currency, and transfer the processed currency into receptacles specific to the corresponding denominations. For example, coin processing machines for processing large quantities of coins from either the public at large or private institutions, such as banks, casinos, supermarkets, and cash-in-transit (CIT) companies, have the ability to receive bulk coins from users of the machine, count and sort the coins, and store the received coins in one or more coin receptacles, such as coin bins or coin bags. One type of currency processing machine is a redemption-type processing machine wherein, after the deposited coins and/or bank notes are counted, funds are returned to the user in a pre-selected manner, such as a payment ticket or voucher, a smartcard, a cash card, a gift card, and the like. Another variation is the deposit-type processing machine where funds which have been deposited by the user are credited to a personal account. Hybrid variations of these machines are also known and available.
A well-known device for processing coins is the disk-type coin sorter. In one exemplary configuration, the coin sorter, which is designed to process a batch of mixed coins by denomination, includes a rotatable disk that is driven by an electric motor. The lower surface of a stationary, annular sorting head is parallel to and spaced slightly from the upper surface of the rotatable disk. The mixed batch of coins is progressively deposited onto the top surface of the rotatable disk. As the disk is rotated, the coins deposited on the top surface thereof tend to slide outwardly due to centrifugal force. As the coins move outwardly, those coins which are lying flat on the top surface of the rotatable disk enter a gap between the disk and the sorting head. The lower surface of the sorting head is formed with an array of exit channels which guide coins of different denominations to different exit locations around the periphery of the disk. The exiting coins, having been sorted by denomination for separate storage, are counted by sensors packed along the exit channel. An example of a disk-type coin sorting mechanism is disclosed in U.S. Pat. No. 5,009,627, to James M. Rasmussen, which is incorporated herein by reference in its entirety and for all purposes.
It is oftentimes desirable in the sorting of coins to discriminate between valid coins and invalid coins. Use of the term “valid coin” can refer to genuine coins of the type to be sorted. Conversely, use of the term “invalid coin” can refer to items in the coin processing unit that are not one of the coins to be sorted. For example, it is common that foreign (or “stranger”) coins and counterfeit coins enter a coin processing system for sorting domestic coin currency. So that such items are not sorted and counted as valid coins, it is helpful to detect and discard these “invalid coins” from the coin processing system. In another application wherein it is desired to process only U.S. quarters, nickels and dimes, all other U.S. coins, including dollar coins, half-dollar coins, pennies, etc., can be considered “invalid.” Additionally, coins from all other coins sets including Canadian coins and European coins, for example, can be considered “invalid” when processing U.S. coins. In another application it may be desirable to separate coins of one country (e.g., Canadian coins) from coins of another country (e.g., U.S. coins). Finally, any truly counterfeit coins (also referred to in the art as “slugs”) are always considered “invalid” regardless of application.
Historically, coins have been sorted and validated or otherwise processed based on physical assessment of their structural characteristics, such as coin diameter, coin thickness, metal content, shape, serrations and engravings on obverse and reverse sides of the coin. To improve discriminating accuracy, coin processing units have been designed for discriminating and authenticating coins by optically detecting coin surface patterns. For example, one known coin discriminating apparatus is provided with an assortment of light emitting elements, such as light emitting diodes (LEDs), for projecting light onto a passing coin, and a photodetector, a charge-coupled device (CCD) detector, or other optical sensor for optically detecting light emitted from the light emitting elements and reflected by the surface of the coin. From the reflected light pattern, the apparatus is able to authenticate and denominate coins based on coin image pattern data that was optically detected and digitized.
One drawback with many prior art optical coin discriminating devices is an undesirably large proportion of discrimination errors caused by variations in coin surface reflectance due to aging and wear. In addition, the processing and remediation time for identifying and removing invalid or unfit coins using many conventional optical coin discriminating devices is undesirably long for bulk coin processing systems that must process thousands of coins within a few minutes. In addition to being slow and unreliable, many prior art optical coin discriminating devices are costly and require a great deal of packaging space with a large window for imaging. Moreover, most optical coin processing systems that are available today utilize single/broad wavelength lighting schemes (e.g., white light) that can only capture limited spectral characteristics of the coins being processed.